vt: keyboard, make keyboard_tasklet local

Now that the last extern user of the tasklet (set_leds) is in
keyboard.c, we can make keyboard_tasklet local to this unit too.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210105120239.28031-2-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>